DESCRIPTION The prostate cancer is the second leading cause of cancer death in men. At early stage, the growth of prostate cancer is androgen-dependent and castration has been a very effective method in treating prostate cancer. Development of androgen-independent growth of prostate cancer after approximately 18 months of hormone ablation therapy is a major clinical dilemma. Goal of this study is to investigate the molecular mechanisms of CKI p21/Cip1/Waf1 in androgen-dependent and -independent growth of prostate carcinoma cells. This study is based on our observations that p21/Cip1/Waf1 gene was up-regulated by androgen and an increased basal expression of the gene was found in an androgen-independent prostate cancer cell line. This proposal will investigate the anti-apoptosis function of p21/Cip1/Waf1 gene in prostate carcinoma cells, which may confer the homeostasis of the cells in androgen-dependent manner and development of androgen-independent growth of pro-static cancer cell by increased basal expression of the gene. The molecular mechanism of androgen action on p21/Cip1/Waf1 gene expression will be elucidated. In addition, an in vivo androgen-independent prostate cancer model will be established for future therapeutic studies. Finally, the expression of the p21/Cip1/Waf1 gene in androgen-dependent and -independent prostate cancer specimens will be evaluated. If indeed an increased basal level of p21/Cip1/Waf1 gene in androgen-independent prostate cancer specimens was observed, it can be served as a clinical marker for developing androgen-dependent growth of prostate cancer.